Simultaneous determination of eight pesticide residues in coconut using MSPD and GC/MS

A simple and effective extraction method based on matrix solid-phase dispersion (MSPD) was developed to determine dimethoate, malathion, lufenuron, carbofuran, 3-hydroxycarbofuran, thiabendazole, difenoconazole and trichlorfon in coconut pulp using gas chromatography-mass spectrometry with selected ion monitoring (GC/MS, SIM). Different parameters of the method were evaluated, such as type of solid-phase (C(18), alumina, silica-gel and Florisil), the amount of solid-phase and eluent (dichloromethane, acetone, ethyl acetate, acetonitrile, n-hexane and n-hexane:ethyl acetate (1:1, v/v)). The best results were obtained using 0.5 g of coconut pulp, 1.0 g of C(18) as dispersant sorbent, 1.0 g of Florisil as clean-up sorbent and acetonitrile saturated with n-hexane as eluting solvent. The method was validated using coconut pulp samples fortified with pesticides at different concentration levels (0.25-1.0 mg kg(-1)). Average recoveries (four replicates) ranged from 70.1% to 98.7%, with relative standard deviations between 2.7% and 14.7%, except for lufenuron and difenoconazole, for which recoveries were 47.2% and 48.2%, respectively. Detection and quantification limits for coconut pulp ranged from 0.02 to 0.17 mg kg(-1) and from 0.15 to 0.25 mg kg(-1), respectively.